Water-cooled electric furnace roof



March 26, 1968 K. w. HANSEN ETAL WATER-COOLED ELECTRIC FURNACE ROOF 5 Sheets-Sheet 1 Filed March 1, 196$ Fig. I

//VV'/V70/?5 KENNETH W- HANSEN %DONALD LiMARTI N n-rromvsr March 26, 1968 w. s ETAL' 3,375,317

WATER-COOLED ELECTRIC FURNACE ROOF Filed March 1, 1965 5 Sheets-Sheet 2 KENNETH w. HANSEN e DONALD 1.. MARTIN March 26, 1968 K. w. HANSEN ETAL 3,375,317

WATER-COOLED ELECTRIC FURNACE ROOF Filed March 1, 1965 5 Sheets-Sheet 3 KENNETH W. HANSEN Q DONALD L. MARTIN ATTORNEY Patented Mar. 26, 1968 3,375,317 WATER-COOLED ELECTRIC FURNACE ROOF Kenneth W. Hansen, Bethel Park, and Donald L. Martin,

Monroeville, Pa., assignors to Harbison-Walker Refractories Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 1, 1965, Ser. No. 436,131 8 Claims. (Cl. 139) The present invention relates to electric furnace refractory roofs and, more particularly, to the provision for cooling of such roofs.

Many metals, ores, and minerals are commercially processed in electric furnaces of different types. Metals are melted, refined, and alloyed and both ferrous and nonferrous ores are reduced in electric furnaces under diverse operating conditions. Steel and iron are the principal products treated in electric furnaces and the amount of nickel, copper, aluminum, zinc, and other nonferrous metals and alloys also add up to large tonnages.

The extremely high temperatures, to which uncooled refractory roofs on electric furnaces are subjected, usually erode or eat them away to such an extent that, within relatively few heats, they have to be replaced by new ones. This not only is expensive but it means that, for the last few heats, the roof may not be rigid and is apt to fall into the furnace. To prolong the life of the refractory roofs or furnaces (by keeping their temperature down to a point at which they are not readily eaten away by the intense heat in the furance), it has been proposed, heretofore, to cool the roofs by strategically arranging pipes within, under, or around the roof, and circulating a cooling liquid, such as water, through the pipes to carry away some of the heat. a

In Del-Buono, US. Patent 2,766,736, an electric furnace roof is disclosed in which a plurality of hollow elements of trapezoidal cross section extend completely across the furnace roof, with refractory material disposed in the spaces between said elements. The roof is generally fiat and contains a common conduit for the inlet and outlet of each element. It should be noted that the hollow elements are not merely embedded in the refractoryhut extend, substantially, through the entire distance or thickness of the roof. In the patent to Schuler, US. 2,271,045, a water-cooled skew is disclosed. Steel Magazine Dec. 9, 1963, page 96, illustrates a rather complex roof cooling syslern consisting of concentric tubing.

It is an object of this invention to provide an improved and novel electric furnace roof construction in which cooling pipes are uniquely arranged with the refractory material ofthe roof, so as to effectively cool the roof and prolong its life by reducing spalling and other deterioration thereof.

Another object of the invention is to provide for the cooling of an electric furnace roof in a more simple, economical, and efiicient manner than was possible heretofore. I

Other objects of the invention will be apparent hereinafter.

In order to more fully understand the nature and scope of the invention, reference should be had to the following detailed description and drawings, in which:

FIG. 1 is an elevation view partly in cross section of a typical electric furnace;

FIG. 2 is a plan view of an electric furnace roof of the present invention;

FIG. 3 is a section taken along line A-A of FIG. 2;

FIG. 4 is a plan view of an alternate furnace roof construction; and

FIG. 5 is an elevation view, partly in cross section, of' a further alternate furnace. roof construction.

- Briefly, in accordance with the present invention, there is provided an electric furnace roof of generally circular, downwardly opening, concave configuration, containing a monolithic refractory material. The roof is provided with a plurality of centrally located, vertical openings therethrough, suitable for accommodating furnace electrodes, and may contain a peripheral or off-center vertical opening for a dust collector port. A plurality of independent U-sha-ped conduits are embedded within the refractory material, so that the apex of each conduit is closely adjacent a central vertical opening. In a preferred embodiment, the apex of certain of the conduits extend within the area delineated by the centrally located vertical openings. The ends of each leg of the conduits extend to a position exterior to said refractory material, so as to define an inlet and an outlet for each conduit. It is preferred that each conduit has a separate control valve (at the inlet and the outlet) to regulate the ingress and egress of cooling fluids, and, also, that the conduits are spaced substantially equal distances apart.

When a dust collector is employed with the electric furnace, a port is provided in the peripheral roof opening, and one of said conduits partially encompasses said port for cooling thereof. A common means is provided, exterior to the refractory material, for supplying a cooling medium to each conduit; and a common means is provided for discharging the cooling medium from each of the conduits.

Referring to FIG. 1, a body of an electric furnace is formed by a metal shell 2, which is circular in horizontal cross section, and which contains a refractory lining 4. One side of the furnace is provided with a door opening 6 and the other side with a pouring spout 8, for the metal melted therein. The top of the furnace is closed byv a removeable dome-like roof 10, having a circular frame 11, and containing a suitable refractory material (not shown). The central portion of the roof is provided .with a plurality of vertical openings, each of which accommodate a furnace electrode 12, that projects down into the furnace. v

With reference to FIGS. 2 and 3, there is shown an electric furnace roof construction suitable for-use with the furnace of FIG. 1, according to one embodiment of the present invention. Only a portion of the roof interior has 'been shown for the sake of simplicity. The roof consists of a circular frame 16. Within the frame is a monolithic refractory material. 18 which may be a plastic, castable, ramming mix or another similar monolith forming material .well known to those skilled in the art.

As is perhaps most clearly shown in FIG. 3, the roof is of generally circular, downwardly opening, concave configuration. The monolithic refractory material is provided with centrally located, circular openings 20, suitable for accommodating furnace electrodes, and an offcenter or peripheral vertical opening 22, having a dust collector port 24 disposed therein, Embedded within the monolithic refractory material 18 are a plurality of spaced, independent U-shaped conduits 26. The apex 27 of certain of the conduits 26a is disposed within the central or delta area of a triangle dilineated by the vertical openings 2%. The apex 28 of the remainder of the conduit-s 26b is disposed exterior to the central area, but closely adjacent a vertical opening 20. One of the conduits 29 partially encompasses the dust collector port 24. All of the conduits have legs 30 and 31 which extend toward the outer periphery of the roof. The ends of each leg 30 of the U-shaped conduits 26 extend upwardly through the refractory material 18,exterior to the roof into a peripheral skew 32, so as to define an inlet 35. The ends of each leg 31 extend directly into the skew to provide an outlet 36 for each conduit. Preferably, the skew is fabricated as part of the outer frame 16 so as to provide an enclosed sectioned channel 38. The channel section 38a contains a cooling medium, such as water, steam, orthe like, which is supplied to the skewsthrough tube 40 from means such as a water pump, steam generator, etc. The circulating coolant flows back to the source via channel section 381) throughtube 41. Each inlet 34 and outlet 36 contains a separate control valve 42 and 44, respectively, for controlling the fiow of cooling mediumthrough the conduits and for emergency shut-off.

In operation, the cooling medium, preferably water, is pumped through the skew channel 38 via section 3-8a'and through. each conduit having an open control valve. The stream of water passes through each conduit independently of the other adjacent conduit, while effectively cooling the furnace roof, whereupon each heated stream is removed at the outlet end 36 of each conduit and passes through channel section 38b (when the outlet control valve 44 is opened). The circulation of the cooling-me dium in this manner is effective for cooling the roof adequately without spalling or other deterioration of the refractory mate-rial immediately beneath the conduits. In the event that there is an uneven distribution of cooling throughout the furnace roof, which may cause some difficult-ies, certain of the control valves may be closed to eliminate that conduit from the Water stream.

In FIG. 4, there is shown another embodiment of the present invention. The circular, downwardly opening concave roof 40 consists of a frame 42 having amonolithic refractory material 44 there within. The monolithic refractory material is provided with a plurality of centrally located, vertical openings 46, therethrough (suitable for accommodating furnace electrodes) and aperipheral, vertical opening 48 (suitable for accommodating a dust collector port 49). A plurality of U-shaped conduits 50, of approximately the same shape and design, are embedded within the refractory material and are spaced substantially equal distances apart from one another. One conduit 52, of slightly different design, partially encompasses the peripheral, vertical opening 48. The apex 54 of all of the conduits is disposed closely adjacent a vertical opening 46. The legs of all the conduits extend towards the outer periphery of the roof 40, similar to the roof of FIG. 2. The roof 40, also contains a peripheral skew 58. The inlet ends 60 of each conduit are connected to a common pipe 62, and the outlet ends 64 of each conduit are attached to a different common pipe 66, both pipes being disposed within the channel of the skew 58. Each inlet and outlet contains a control valve 68 and 70.

In operation, the cooling medium, prefer-ably water, is pumped into the common tubing 62 (-by means of a channel 70 from a source of coolant sup-ply), passes through the common tubing and into the conduits at the inlet ends 60 (which are opened) through the conduits, and is discharged at the open outlet ends 64 of each conduit into the common tubing 66. The water stream is then circulated back through a channel 72 to the source of supply. Here also, a separate stream of water passes through each conduit independently ofthe other'adjacent conduits.

7 Referring to FIG. 5, there is shown a cross-sectional view of a further embodiment of the invention. The roof in FIG. is similar to that of FIG. 4 with two exceptions. First, the legs 75 of each conduit 76 are disposed in the vertical plane of the furnace roof, as distinguished from the roofs of FIGS. 2 and 4, which legs are in the horizontal plane of the roof. This latter arrangement is thought to strengthen the refractory monolithic material 78. The other difference is that only the inlet ends 80 of each conduit contain a control valve 82. As is shown, both the inlet 80 and the outlet 84 are connected to a separate common cooling tube 86 and 88, respectively. However,

1 v both the inlet and outlet ay be connected to cooled skew as shown in FIGS. 2 and 3.

It should be appreciated that with the disposition of cooling conduits in the present invention especially the embodiments of FIGS. 2 and 3, the central area closely adjacent the electrode openings is adequately cooled without the necessity for additional cooling means. Such an arrangement also precludes the occurence of a magnetic field around the electrodes which is possible with spiral or helical conduit cooling systems that completely envelop the electrodes. Further, the present invention obviates the use of special refractory shapes which add to the cost of an electric furnace roof.

Since certain changes in carryingout the above invention may be made without departing from its scope, it is intended that the accompanying description and drawings be interpreted as illustrative and not in limitation of the invention.

Having thus described the invention in detail and with sufficient particularity as to enable those skilled in the art to practice it, what is desired to have protected by Letter Patent is set forth in the following claims:

We claim:

1. In an electric furnace, a circular roof containing a monolithic refractory material and provided with a plurality of centrally located vertical openings therethrough, an electrode disposed in each opening, a plurality of independent U-shaped conduits embedded entirely with in said refractory material, said conduits being characterized by having an apex disposed closely adjacent an electrode and legs extending toward the outer periphery of the roof, said conduits being spaced substantially equal distances apart from one another, the ends of each leg of said U-shaped conduits extending through the refractory a watermate-rial and exterior thereto along the outer periphery thereof so as to define an inlet and an outlet for each conduit, each inlet and outlet having a separate control valve, a common tubing attached to each inlet for discharging the cooling medium from said conduits.

Z. In an electric furnace, a roof of generally circular, downwardly opening concave configuration containing a monolithic refractory materal provided with a plurality of centrally located vertical openings therethrough suitable for accommodating furnace electrodes, a plurality of independent U-shaped conduits embedded entirely within said refractory material, said conduits being characterized by having an apex disposed closely adjacent a vertical opening and legs extending toward the outer periphery of the roof, the ends of each leg of said U-shaped conduits extending exterior to said refractory monolith to define an inlet and outlet for said conduits, means common to each inlet and attached thereto for supplying a cooling medium to said conduits, and means common to each outlet and attached thereto for discharging said cooling medium from said conduits.

3.In a roof for an electric furnace, a circular frame including an outer peripheral skew containing a cooling medium, monolithic refractory material within the frame, a plurality of U-shaped conduitsembedded entirely within said refractory material, said conduits being independent and spaced substantially equal distances apart from one another, said conduits being characterized by having an apex disposed closely adjacent an electrode and legs extending toward the outer periphery of the roof, the

'ends of each leg of said U-shaped conduits extending upwardly through the refractory material exterior to the roof and into said peripheral skew so as to define an inlet and an outlet for each conduit, each inlet and outlet having a separate control valve for supplying the cooling medium to said conduits and for discharging the cooling medium from said conduits.

4. In a roof for an electric furnace, a circular frame, monolithic refractory material within the frame provided with a plurality of centrally located vertical openings therethrough, an electrode disposed in each opening, a

plurality of spaced independent U-shaped conduits embedded within said monolithic refractory material, certain of said conduits being characterized by having an apex disposed within the central area delineated by said vertical openings, the remainder of said conduits characterized by having an apex disposed exterior to said central area but closely adjacent an electrode, all of said conduits being further characterized by having legs extending toward the outer periphery of the roof, the ends of each leg of said U-shaped conduits extending exterior to the refractory material to define an inlet and outlet for each conduit, means common to each inlet and attached thereto for supplying a cooling medium to said conduits and means common to each outlet and attached thereto for discharging said cooling medium from said conduits.

5. An electric furnace roof of generally circular downwardly opening concave configuration, having a central area including a plurality of circular openings and an outer peripheral skew containing a cooling medium, an electrode disposed in each opening, a plurality of independent U-shaped conduits embedded entirely within said monolithic refractory material, certain of said conduits being characterized by having an apex disposed within said central area, the remainder of said conduits characterized by having an apex disposed exterior to said central area but closely adjacent an electrode, all of said conduits 'being further characterized by having legs extending toward the outer periphery of the roof, the ends of each leg of said U-shaped conduits extending vertically through the refractory material exterior to the roof and into said peripheral skew, so as to define an inlet and outlet for each conduit, each inlet and outlet having a separate control valve for supplying the cooling medium to said conduits and for discharging said cooling medium from said conduits.

6. In an electric furnace, a circular roof containing a monolithic refractory material and provided with a plurality of centrally located vertical openings and at least one off-center vertical opening therethrough, an electrode disposed in each central opening, a dust collector channel disposed in said olf-center opening, a plurality of independent U-shaped conduits embedded entirely within said refractory material, said conduits being characterized by having an apex disposed closely adjacent an electrode and legs extending toward the outer periphery of the roof, one of said conduits partially encompassing said dust collector channel, the ends of each leg of said U-shaped conduits extending upwardly through the refractory material exterior to the roof and along the outer periphery thereof so as to define an inlet and an outlet for each conduit, each inlet and outlet having a separate control valve, a

tubing common to each inlet and attached thereto for,

supplying a cooling medium to said conduits, and a tubing common to each outlet and attached thereto for discharging the cooling medium from said conduits.

7. In a roof for an electric furnace, a circular frame, monolithic refractory material within the frame provided with a plurality of centrally located vertical openings and at least one off-center vertical opening therethrough, an electrode disposed in each central opening, a dust collector channel disposed in said off-center opening, a plurality of spaced independent U-shaped conduits embedded entirely within said monolithic refractory material, certain of said conduits being characterized by having an apex disposed within the area delineated by said centrally located vertical openings, the remainder of said conduits being characterized by having an apex disposed exterior to said area but closely adjacent an electrode, all of said conduits being further characterized by having legs extending toward the outer periphery of the roof, one of said conduits partially encompassing said dust collector channel, the ends of each leg of said U-shaped conduits extending exterior to the roof to define an inlet and outlet for each conduit, means common to each inlet and attached thereto for supplying a cooling medium to said conduits and means common to each outlet and attached thereto for discharging said cooling medium from said conduits.

8. An electric furnace roof of generally circular downwardly opening concave configuration, containing a monolithic refractory material having a central area provided with a plurality of vertical openings and at least one vertical opening adjacent said central area and an outer peripheral skew containing a cooling medium, an electrode disposed in each opening in said central area and a dust collector channel disposed in said adjacent opening, a plurality of independent U-shaped conduits embedded entirely within said monolithic refractory material, certain of said conduits being characterized by having an apex disposed within said central area, the remainder of said conduits being characterized by having an apex disposed exterior to said central area but closely adjacent an electrode, all of said conduits being further characterized by having legs extending toward the outer periphery of the roof, one of said conduits partially encompassing said dust collector channel, the ends of each leg of said U-shaped conduits extending upwardly through the refractory material exterior to the roof and into said peripheral skew, so as to define an inlet and outlet for each conduit, each inlet and outlet having a separate control valve for supplying the cooling medium to said conduits and for discharging said cooling medium from said conduits.

References Cited UNITED STATES PATENTS 2,186,740 1/1940 Teeters 26546 X 2,766,736 10/1956 Del-Buono l3-9 X 648,714 8/1953 Williams et a1 263-44 X 3,247,829 4/1966 Mort-on l226 BERNARD A. GILHEANY, Primary Examiner. H. B. GILSON, Assistant Examiner. 

1. IN AN ELECTRIC FURNACE, A CIRCULAR ROOF CONTAINING A MONOLITHIC REFRACTORY MATERIAL AND PROVIDED WITH A PLURALITY OF CENTRALLY LOCATED VERTICAL OPENINGS THERETHROUGH, AN ELECTRODE DISPOSED IN EACH OPENING, A PLURALITY OF INDEPENDENT U-SHAPED CONDUITS EMBEDDED ENTIRELY WITHIN SAID REFRACTORY MATERIAL, SAID CONDUITS BEING CHARACTERIZED BY HAVING AN APEX DISPOSED CLOSELY ADJACENT AN ELECTRODE AND LEGS EXTENDING TOWARD THE OUTER PERIPHERY OF THE ROOF, SAID CONDUITS BEING SPACED SUBSTANTIALLY EQUAL DISTANCES APART FROM ONE ANOTHER, THE ENDS OF EACH LEG OF SAID U-SHAPED CONDUITS EXTENDING THROUGH THE REFRACTORY MATERIAL AND EXTERIOR THERETO ALONG THE OUTER PERIPHERY THEREOF SO AS TO DEFINE AN INLET AND AN OUTLET FOR EACH CONDUIT, EACH INLET AND OUTLET HAVING A SEPARATE CONTROL VALVE, A COMMON TUBING ATTACHED TO EACH INLET FOR DISCHARGING THE COOLING MEDIUM FROM SAID CONDUITS. 